A : Dictyotene stage occurs in female only.
R : Gametogenesis rests for a long period at diplotene stage in female.

Options

A. IF both Assertion & Reason are true and the reason followed is the correct explanation of the assertion then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statement then mark (4).

Answer

To solve the assertion-reason question, we need to evaluate both statements and determine their truthfulness and relationship.

### Step-by-step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the Dictyotene stage occurs only in females.
- This is true because the Dictyotene stage is a specific phase of oogenesis (the formation of ova) in females, where primary oocytes are arrested in prophase I of meiosis. Males do not have this stage in their spermatogenesis.

2. **Understanding the Reason (R)**:
- The reason states that gametogenesis rests for a long period at the diplotene stage in females.
- This is also true. In females, primary oocytes remain in the diplotene stage (which is synonymous with the Dictyotene stage) for many years, often until puberty when they resume meiosis.

3. **Evaluating the Relationship**:
- We need to determine if the reason correctly explains the assertion. Since the Dictyotene stage is a prolonged diplotene stage where gametogenesis is arrested, the reason indeed explains why the assertion is true. The prolonged arrest in this stage is unique to females and is a key characteristic of their reproductive biology.

4. **Conclusion**:
- Both the assertion and the reason are true, and the reason provides a correct explanation for the assertion.
- Therefore, the correct answer is that both A and R are true, and R is the correct explanation of A.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation of the assertion.

---